This is an archived document. The links are no longer being updated.
TB Notes 1, 2000
Thoughts about the Future of TB Control in the United States
by Charles M. Nolan, MD
Director, TB Control Program
Seattle-King County Dept of Public Health
It is gratifying, isn't it, to be back on the pathway toward TB
elimination. I guess it's true that we who work in TB control had
more prominence and visibility in the recent era during which TB
was resurgent; a declining public health problem is never very newsworthy.
Still, speaking personally, the satisfaction of watching the regular
declines in US TB morbidity each year since 1992 exceeds the cheap
thrill of being interviewed by local TV news personalities about
the looming threat to our community of resurgent TB.
But what does the future hold for TB controllers? Will we continue
to see our efforts rewarded by predictable declines in TB case numbers
and rates into the indefinite future, until we finally arrive at
our goal, the elimination of TB from the US? Even though we are
good people, working toward a noble cause that we deserve to achieve,
I submit that this optimistic view of an inevitable future decline
of TB in the US is not necessarily our destiny. I fear that as we
continue to work against TB in its current epidemiological expression
in the US, we may be destined to reach a point at which the force
of TB control is balanced by the force of the disease in our population.
In that scenario, with neither opposing force having the upper hand,
TB morbidity in the US will not continue to decline but will become
I am emboldened to hypothesize, in the absence of new factors in
the equation, a forthcoming equilibrium between TB and TB control
in the US, and a stabilization in the TB incidence rate in the US,
because that is precisely what has happened in recent years in my
community. The accompanying figure portrays the
numbers of TB cases reported in Seattle-King County, Washington,
and in the US from 1990 through 1998. Even though the numbers of
cases represented in the two jurisdictions differ dramatically,
the trend is unmistakable; during a period in which the TB morbidity
in the US declined by 35%, that in Seattle-King County remained
basically stable. (If annual incidence rates rather than case numbers
had been presented, the trends would have been the same).
Image 1: Graph showing the Tuberculosis in Seattle-King County
1990-1998; Comparison with U.S. TB Morbidity.
Here is my explanation for the trends shown in the figure. At the
national level, we are now reaping the harvest of reinvesting in
good TB control. We have secured the necessary funding and have
applied those funds strategically throughout the country to strengthen
surveillance and case finding, to expand directly observed therapy
for TB cases in order to increase completion rates and reduce acquired
drug resistance, and to stop nosocomial transmission and other pockets
of current transmission of TB.
Speaking in terms of a theory of TB control, our investment has
allowed us to regain the ground that was lost during the resurgence
by applying to their best advantage our current tools (this fact
was noted in a JAMA editorial written in 1997 by Drs. Bess
Miller and Ken Castro of the Division of TB Elimination). In that
sense, the drop in cases and case rates nationally represent a reduction
in "excess morbidity" that arose during the time when
the national infrastructure was weakened in relation to the strength
of the dual epidemics of TB and HIV, increased immigration from
high-prevalence areas, and person-to-person transmission of TB,
including nosocomial transmission.
Some places such as Seattle, however, did not experience the full
power of the TB resurgence. For example, we were only modestly impacted
by the HIV/TB phenomenon, with rapid person-to-person spread of
disease, and MDR TB. Our infrastructure had not been dismantled,
and we experienced less excess morbidity in those bad days. In the
decade of the 1990s, however, even though we believe we have a good
program structure, a talented staff, and funding sufficient to allow
us to do good TB control work, we have failed to effect a meaningful
reduction in TB morbidity in our community. In other words, we appear
to have reached an equilibrium with our target disease, given its
current epidemiological pattern in our community. This experience
is the basis for my suggestion that it is possible that the nation
as a whole will also reach such an equilibrium point, once its excess
TB morbidity has been "mopped up." When that point may
be reached, and at what level of morbidity, I of course cannot say.
I don't want to leave the impression that we have passively accepted
the current status quo in Seattle. We are aggressively
attempting to disrupt the equilibrium between TB and TB control
by learning more about the epidemiology of TB in our community and
by increasing the effectiveness of our community-based TB control
plan. For example, in our community, persons born outside the US
account for 70%-75% of cases, and RFLP survey data suggest that
nearly all of our cases in foreign-born persons arise through reactivation
of latent infection, including persons who have received preventive
therapy. This information suggests that we need to expand treatment
of latent TB infection in high-risk foreign-born persons; to accomplish
that, we have established a Preventive Therapy Partnership Program
with a number of health care facilities that provide primary health
care to high-risk foreign-born persons. Also, given that we regularly
see TB occur in foreign-born persons who have received preventive
therapy in the past, we are reevaluating the traditional approach
to preventive therapy, and have secured funding to develop new approaches
to increase the uptake and completion of preventive therapy by newly-arrived
immigrants and refugees.
Should the nation encounter such a "mud hole" in the
road to TB elimination, similar strategies will be required to move
beyond it. ACET, in its recent publication, TB Elimination Revisited:
Obstacles, Opportunities, and a Renewed Commitment, has made
several practical suggestions, including the need for every locale
and/or state to understand the unique nature of its own TB problem,
in order to apply current tools for TB control to their best advantage.
The establishment of new partnerships to reach locally-identified
high-risk groups is another important new concept.
Another way that an equilibrium between TB and TB control may become
tipped in favor of TB control is by the introduction of new tools
for the diagnosis, treatment, or prevention of TB. This point was
also made by Dr. Miller and Dr. Castro in their JAMA editorial.
Consider, for example, the advantage of being able to identify,
among a population of 100 persons screened and found to have positive
tuberculin skin tests, the handful that are destined to develop
TB in the future, and to offer treatment only to those who are truly
at risk, rather than to the entire cohort.
Likewise, based on forthcoming ATS/CDC recommendations, we now
have a range of options for treatment for latent TB infection, which
should result in more effective use of that preventive intervention.
Finally, given the events of the past year, with burgeoning interest
in a TB vaccine on the part of the US government, private philanthropic
organizations, and the pharmaceutical industry, the notion of a
TB vaccine at last (in the immortal words of Ken Castro) "passes
the laugh test."
Even as Seattle's current impasse with TB has served to motivate
us to redouble our efforts, to think creatively, and to engage new
partners in our struggle, I am confident that, should our trend
become a national one, the nation will be equal to that challenge.
"The man (or woman) who is tenacious of purpose is not shaken
from his firm resolve by the tyrant's threatening countenance."
Horace, 23 BC.